Heat exchanger

ABSTRACT

A heat exchanger is provided comprising a stack of heat exchanger plates ( 1, 1   a,    1   b,    1   c ) formed of sheet metal having a three-dimensional structured pattern ( 2, 3 ), each heat exchanger plate ( 1, 1   a,    1   b,    1   c ) having a groove ( 10 ), a gasket ( 9 ) being arranged in said groove ( 10 ) and resting against an adjacent heat exchanger plate ( 1   a ), said groove ( 10 ) having a bottom inner surface ( 11 ), said inner surfacebottom ( 11 ) having at least a protrusion ( 14, 15 ) directed to said adjacent heat exchanger plate ( 1   a ). It is intended to minimize the risk of a leakage. To this end in the region of said protrusion ( 14, 15 ) said gasket ( 9 ) is compressed more than in a region out of said protrusion ( 14, 15 ).

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/751,208 filed Jan. 28, 2013 which claims foreign priority benefitsunder U.S.C. § 119 from Danish Patent Application No. PA 2012 00103filed on Feb. 7, 2012, the contents of both applications areincorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a heat exchanger comprising a stack ofheat exchanger plates formed of sheet metal having a three-dimensionalstructured pattern, each heat exchanger plate having a groove, a gasketbeing arranged in said groove and resting against an adjacent heatexchanger plate, said groove having a bottom, said bottom having atleast a protrusion directed to said adjacent heat exchanger plate.

BACKGROUND

Such a heat exchanger is known from U.S. Pat. No. 7,490,660 B2. Thegasket has a recess which fits to the protrusion. At the side facing theadjacent heat exchanger plate the gasket has a protrusion fitting in arecess which is formed on the lower side of the adjacent heat exchangerplate. The recess is the negative form of the protrusion on the upperside of the adjacent heat exchanger plate.

The space between the heat exchanger plate and the adjacent heatexchanger plate forms part of the primary flow path or part of asecondary flow path through the heat exchanger. The gasket seals theflow path from the outside or in the region of supply and returnopenings of the heat exchanger plates from the other flow path.

In order to achieve a good heat transfer from one flow path to the otherflow path the heat exchanger plates are relatively thin. This causes aproblem in that the pressure of the fluid within a flow path may deformthe heat exchanger plate. This is especially the case in the area aroundthe openings forming a supply or a return opening, respectively, of therespective flow paths. In the region of these openings, there is in manycases no sufficient connection between a heat exchanger plate and theadjacent heat exchanger plate.

The solution disclosed in U.S. Pat. No. 7,490,660 B2 helps to keep thegasket in position, i.e. between the groove of the heat exchanger plateand in the recess of the adjacent heat exchanger plate. Furthermore, thesealing line has been made longer than without the recesses andprotrusions. However, when the heat exchanger plate deforms under thepressure in one of the flow paths, there is still the risk of a leakagewhen the heat exchanger plate is lifted off the gasket. In this case anopening may appear between the recesses and the gasket, thus givingleaks.

SUMMARY

The task underlying the invention is to minimize the risk of a leakage.

This task is solved in that in the region of said protrusion said gasketis compressed more than in a region out of said protrusion.

When the gasket is mounted between two heat exchanger plates, i.e.between a heat exchanger plate and the adjacent heat exchanger plate,the gasket is compressed a bit in order to rest against a inner surface,such as the top or bottom, of the groove and the lower or upper side ofthe adjacent heat exchanger plate. However, in the region of theprotrusion the protrusion is pressed into the gasket compressing thegasket more than in other regions. To achieve this stronger compressionthe protrusion is pressed into the gasket with a greater force than inother regions. Even in case the heat exchanger plate or plates deform,the protrusion can move a little bit without leaving contact to thegasket. They form an extra barrier against leaking fluids. Theelasticity of the material forming the gasket will just follow theprotrusion still forming a fluid tight barrier. Furthermore, theprotrusion will push at the gasket that still squeezing it against theadjacent heat exchanger plate even at significant deformation of theplates.

In a preferred embodiment said adjacent heat exchanger plate comprises alower side facing said heat exchanger plate, a recess being formed insaid lower side in the region of the protrusion of said adjacent heatexchanger plate, said gasket being deformed into said recess. In otherwords, the recess on the lower side of the adjacent heat exchanger plateis the “opposite” form of the protrusion of the upper side of the heatexchanger plate. When the two heat exchanger plates are stacked ontoeach other the gasket is not only deformed on the side of the heatexchanger plate, but also on the side of the adjacent heat exchangerplate. In this region a gasket is pressed into the recess. Even when theadjacent heat exchanger plate is deformed, the elastic material of thegasket can follow this deformation.

Preferably said protrusion has a height of at least 25% of the thicknessof said gasket. The protrusion is pressed over a rather long distanceinto said gasket so that even heavy deformations do not cause a risk ofa leakage.

Preferably said protrusion has at least at the top a triangular form.The top of the triangle forms an edge. This edge should not be too sharpin order not to destroy the gasket. However, this edge is pressed with arather small area into the gasket so that a great pressure can berealized.

In a preferred embodiment said protrusion has a triangular form. Inother words, the complete protrusion is in the form of a triangle.

In a preferred embodiment said protrusion runs along a curved path. Thecurvature of the curve is parallel to the plane of the heat exchangerplate. This has the further advantage of strengthening the heatexchanger plate.

In a preferred embodiment said heat exchanger plate comprises at leastone through-opening and said protrusion runs along a part of the groovesurrounding said through-opening partly. As mentioned above, in theregion of the through-opening there is the greatest risk of deformationof the heat exchanger plates. In most cases it is sufficient to have theprotrusions only in this area and to keep simple the form of the groovesin other areas.

Preferably said groove comprises at least a linear section runningparallel to an edge of said heat exchanger plate, said protrusion endingout of said linear section. Usually the heat exchanger plates can beconnected along their edges by welding or brazing so that the risk of adeformation of the plates leading to a leakage is rather small in thisarea. Therefore, the form of the groove in an area along an edge can bekept simple.

Preferably said groove comprises side walls and the bottom of the grooveis flat between said side walls and said protrusion. The flat area ofthe groove can be used to squeeze the gasket only a little bit. In thisarea there is only a small load on the gasket so that the stacking ofthe plate can be made without larger forces. However, there is generateda sufficient long sealing line auxiliar to said gasket.

In a preferred embodiment at least two protrusions are arranged in saidgroove, the bottom of said groove being flat between said protrusions.The reason is the same as mentioned before for the area between theprotrusion and the side walls.

In a preferred embodiment at least an auxiliary protrusion is arrangedin said groove, said auxiliary protrusion traversing said grooveorthogonal to said protrusion. It is a possibility to strengthen theplate in the orthogonal direction of the groove further.

Preferably said protrusion is pressed out of the sheet metal of the heatexchanger plate. Therefore, no additional material is necessary.

In a further preferred embodiment, the grooves instead are ‘upwards’hollows, the inner surfaces being a top. The gasket then rests on thisraised section, being the top of the raised section of the lower heatexchanger plate, and this lower section then has protrusions reachinginto the hollows forming the grooves, thus pressing the gaskets into thehollows deforming it as described above. This embodiment naturally alsoapplies to any of the other embodiments as described.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred examples of the invention will now be described in moredetail with reference of the drawing, wherein:

FIG. 1 shows a heat exchanger plate of a heat exchanger stack,

FIGS. 2A and 2B are schematic illustrations to show the form of heatexchanger plates in the region of a gasket groove;

FIG. 3 shows an enlarged view of the detail III of FIG. 1;

FIG. 4 is an alternative embodiment to the embodiment shown in FIG. 3;and

FIG. 5 is an alternate embodiment of FIG. 2A.

DETAILED DESCRIPTION

FIG. 1 shows a heat exchanger plate 1. The heat exchanger plate 1comprises bulges 2 which are raised by a given height over the plane ofthe heat exchanger plate 1. Furthermore, the heat exchanger plate 1comprises hollows 3 which are sunk to a given depth in this heatexchanger plate 1. The bulges 2 are symbolized by white circles whilethe hollows 3 are symbolized by circles with a cross.

As it is known in the art, two such heat exchanger plates 1 form a pairof plates when stacked upon each other. Two such neighbouring platesusually will with be slightly differently shaped, such that when theyare stacked, the bulge 2 of one plate meets with hollows 3 of theneighbouring plate, etc.

Flow paths are in this manner formed within such pairs. Typically theflow path formed on one side of a heat exchanger plate 1 will belong toa first flow path, and the flow path formed on the opposite side willbelong to a second flow path being sealed from the first flow path.

The heat exchanger plate 1 is made of sheet metal. A sheet metal is amaterial having a good thermal conductivity and can be formed in a pressor die. It is also possible to use plastic materials as sheet metal. Thebulges 2 and the hollows 3 form a three-dimensional structured profileor pattern. This pattern is produced in said press or die. However, anyother suitable pattern can be used, e.g. a herringbone pattern, as theyare well established in the art.

The heat exchanger plate 1 of the illustration comprises fourthrough-openings 5-8. These through-openings 5-8 are used to formchannels or connections to the first and second flow paths respectively.For example, the through-openings 5, 7 forms a supply and a return forthe first flow path and the through-openings 6, 8 form a supply and areturn for the second fluid path.

In order to separate the two flow paths from each other a gasket 9 isintroduced between two heat exchanger plates. This is shown in FIG. 2a,2b . FIG. 2 shows three heat exchanger plates 1 a, 1 b, 1 c. To simplifythe further explanation the heat exchanger plate lb is simply termed as“heat exchanger plate” or “first heat exchanger plate”. The heatexchanger plate 1 a is termed as “adjacent heat exchanger plate” or“second heat exchanger plate”.

The gasket 9 has a form that a first set of through-openings 5, 7 isarranged outside a space sealed by the gasket 9 and a second set ofthrough-openings 6, 8 is arranged within the sealing, thus forming e.g.second flow path. The corresponding gasket between the first heatexchanger plate 1 b and a third heat exchanger plate 1 c is positionedsuch the openings 5, 7 are sealed, and the openings 6, 8 are left freeto the external. In this way it is possible to use the through-openings5, 7 as supply and return for the first flow path and thethrough-openings 6, 8 as supply and return for the second flow path.

The gasket 9 is arranged within a groove 10. This groove is shown inmore detail in FIG. 2.

The groove 10 has a inner surface 11, in the present illustration beinga bottom, and two side walls 12, 13. Two protrusions 14, 15 of thegroove 10 of the first heat exchanger plate 1 b are directed to theadjacent or second heat exchanger plate 1 a. In its opposite or lowerside the first heat exchanger plate 1 b comprises two recesses 16, 17 inthe form of which corresponds to the form of the protrusions 14, 15which is in the present case a triangle. However, it is possible thatonly the top of the protrusions is formed as a triangle.

When two heat exchanger plates 1 a, 1 b are stacked onto each other andthe gasket 9 is positioned in the groove 10 of the first heat exchangerplate 1 b, the gasket 9 is deformed in the region of the protrusions 14,15. This deformation results in a compression of the gasket 9 which isstronger in the region of the protrusions 14, 15 than in other regions.To this end the protrusions 14, 15 have a height which ensures asignificant deformation of the gasket 9, such as at least 10% 25% of thethickness of the gasket 9, or more preferably at least 20%, or even morepreferably at least 25%.

The gasket 9 is deformed into the recesses 16, 17 on the lower side ofthe second heat exchanger plate 1 a.

Therefore, the gasket has a wave like form with regions of strongercompression and regions of a less strong compression.

The inner surface 11 of the groove 10 is flat between the side walls 12,13 and the protrusions 14, 15. The bottom 11 of the groove 10 is flat aswell as between the protrusions 14, 15. In these flat regions (the lowerside of the bottom 11 of the groove 10 is flat as well as in theseregions) have the effect that the gasket 9 is only slightly compressedin these regions as it is known from the art.

The effect of the protrusions 14, 15 is shown in FIG. 2b . Even when thefirst heat exchanger plate 1 b is deformed under the pressure betweenthe heat exchanger plates 1 a, 1 b the gasket 9 ensures a tight sealing.Although the heat exchanger plate lb has been deformed, the protrusions14, 15 are still positioned within the gasket 9. The elasticity of thematerial forming the gasket will just follow the protrusions 14, 15still forming a fluid tight barrier. The protrusions 14, 15 will push atthe gasket 9 thus still squeezing it against the second heat exchangerplate 1 a, even at a significant deformation of the heat exchanger plate1 b.

FIG. 3 shows a detail III of FIG. 1 in a larger scale without the gasket9. It can be seen that the protrusions 14, 15 in the groove 10 arerestricted to a section of the groove 10 surrounding the through-opening5 partly. Therefore, the protrusions 14, 15 run along a curved path thusstrengthening the heat exchanger plate 1. The groove 10 has at least alinear section 18, 19 running along the edges of the heat exchangerplate 1. The protrusions 14, 15 are restricted to an area out of saidlinear sections 18, 19.

In FIG. 4 a slightly modified embodiment is shown. The same elementshave the same reference numerals. In FIG. 4 the gasket is not shown.

Auxiliary protrusions 20 are arranged in the groove 10. These auxiliaryprotrusions 20 traverse the groove 10 orthogonal to the protrusions 14,15. These auxiliary protrusions 20 serve to strengthen the heatexchanger plate 1 in the orthogonal direction too.

FIG. 5 shows an alternative embodiment where the grooves 10 instead are‘upwards’ hollows within the walls 12, 13 forming a raised section, theinner surface 11 being a top. The gasket 9 then rests on this raisedsection, being the top 11 of the raised section of the lower heatexchanger plate, and this lower section then has protrusions 14, 15reaching into the hollows forming the grooves 10, thus pressing thegaskets 9 into the hollows deforming it as described above.

Any of the embodiments of the FIGS. 1-4 also applies to this embodimentof FIG. 5.

While the present disclosure has been illustrated and described withrespect to a particular embodiment thereof, it should be appreciated bythose of ordinary skill in the art that various modifications to thisdisclosure may be made without departing from the spirit and scope ofthe present disclosure. What is claimed is:

1. A heat exchanger comprising a stack of heat exchanger plates formedof sheet metal having a three-dimensional structured pattern, each heatexchanger plate having a groove, a gasket being arranged in said grooveand resting against an adjacent heat exchanger plate, said groove havinga bottom inner surface, said inner surfacebottom having at least aprotrusion directed to said adjacent heat exchanger plate, wherein inthe region of said protrusion said gasket is compressed more than in aregion out of said protrusion.
 2. The heat exchanger according to claim1, wherein said adjacent heat exchanger plate comprises a lower sidefacing said heat exchanger plate, a recess being formed in said lowerside in the region of the protrusion of said adjacent heat exchangerplate, said gasket being deformed into said recess.
 3. The heatexchanger according to claim 1, wherein said protrusion has a height ofat least 10% of the thickness of said gasket.
 4. The heat exchangeraccording to claim 3, wherein said protrusions has a height of at least15% of the thickness of said gasket.
 5. The heat exchanger according toclaim 1, wherein said protrusion has at least at the top a triangularform.
 6. The heat exchanger according to claim 1, wherein saidprotrusion has a triangular form.
 7. The heat exchanger according toclaim 1, wherein said protrusion runs along a curved path.
 8. The heatexchanger according to claim 1, wherein said heat exchanger platecomprises at least one through-opening and said protrusion runs along apart of the groove surrounding said through-opening partly.
 9. The heatexchanger according to claim 1, wherein said groove comprises at least alinear section running parallel to an edge of said heat exchanger plate,said protrusion ending out of said linear section.
 10. The heatexchanger according to claim 1, wherein said groove comprises side wallsand the bottom inner surface of the groove is flat between said sidewalls and said protrusion.
 11. The heat exchanger according to claim 1,wherein at least two protrusions are arranged in said groove, the bottominner surface of said groove being flat between said protrusions. 12.The heat exchanger according to claim 1, wherein said protrusion ispressed out of the sheet metal of the heat exchanger plate.
 13. The heatexchanger according to claim 1, wherein grooves are formed as a hollowthe walls forming lowered sections, and the inner surface being abottom.
 14. The heat exchanger according to claim 1, wherein grooves areformed as a hollow the walls forming raised sections, and the innersurface being a top.
 15. The heat exchanger according to claim 2,wherein said protrusion has a height of at least 10% of the thickness ofsaid gasket.
 16. The heat exchanger according to claim 3, wherein saidprotrusion has a height of at least 25% of the thickness of said gasket.